Improving Methane Production From Food Waste By Using Fe And Fe/C

Acidification in the anaerobic fermentation of food waste causes the pH value to decrease,the system to become unstable,and the methane production performance to be affected.In order to improve the quality of anaerobic fermentation,this study analyzed the formation and transformation mechanism of volatile fatty acids(VFAs)under different F/M(Food/Mud),explored the release effect of exogenous substances on the methane inhibition effect of high F/M food waste,and determined the optimal dosage of exogenous substances.The yield of acetic acid and butyric acid,which can be directly utilized by microorganisms,is optimized by response surface methodology.Based on the above results,the methane production performance of the two phase anaerobic fermentation system is improved by adding exogenous substances to the acidified and methane phase,and the stability of the system is optimized under the optimal acidification conditions.Firstly,using different F/M(VS/VS)(0.5,1,2,2.5,3,4)to produce acid and gas production under the anaerobic fermentation of kitchen waste,the inhibitory effect of F/M on methane production was significant,the biodegradation rate was lower than 34.52%and the methane production rate was only 5.62 mL·(gVS)-1·d-1.By adding zero valent iron with exogenous additives,when the F/M is less than 2,the cumulative methane production and biodegradation rate have increased significantly.When the addition of zero valent iron is greater than or equal to 6 g·L-1,the biodegradation rate increases to more than 70%,and the cumulative methane production of the load increases to more than 440 mg· L-1.In addition,the response surface method was used to optimize the anaerobic fermentation conditions for food waste fermentation.In order to provide direct use of acetic acid and butyric acid concentration and response value,the temperature was 41.67,F/M was 2,the initial pH value was 9,HRT was 3.35 d,and OL was 80(gVS)·L-1,the best acid production effect.Under this technological condition,the concentration of butyric acid and acetic acid reached 19324.7 mg·L-1,accounting for 89%of the total VFAs.The study on the effect of acid production under different technological conditions was studied.When the initial pH value was 9,the pH change of the system was maintained within the optimum pH range of the hydrolytic acidified bacteria,and the effect of acid production was higher.Medium and high temperature is more suitable for the survival of acid producing bacteria,and the system stability and acid production ability are higher than those of the super high temperature.When OL was 50(gVS)·L-1,the activity of hydrolytic acidification bacteria is stronger,and a higher level of VFA can be obtained.When F/M is 2,pH decreases slowly,pH stays between 5.8?6.3,and the acid production was good,but the pH range is not conducive to the growth of methanogensFinally,the effect of Exogenous Additives on two-phase anaerobic digestion was studied under the condition of optimal acidification as the raw material of two-phase anaerobic methanation.The effect of Exogenous Additives Fe and Fe/C on the accumulation of methane production,methane production rate and biodegradation rate of the two phase anaerobic fermentation was significant,and the main effect was in the acidification stage.The amount of methane produced by acidification plus Fe and two phase whole process plus Fe is 457.56 and 448.99 mL(gVS)-1,and the biodegradation rate reached 84.11%and 82.53%respectively.The amount of methane produced by acidification plus Fe/C and two phase whole process plus Fe/C is 474.94 and 487.30 mL·(gVS)-1,and the biodegradation rate reached 87.30%and 87.58%respectively.It shows that the effect of exogenous substances mainly acts on the acidification stage.Moreover,the biogas production of exogenous substance Fe/C is stronger than that of exogenous substance Fe.The enzyme activity also increased significantly with the addition of Exogenous Additives.In the two-phase fermentation system,the concentration of DHA was between 2.23?2.95 mg·g-1·h-1,and the concentration of coenzyme F420 was between 0.0063-0.0294 ?mol(gVS)-1,indicating that the enzyme activity of the anaerobic fermentation system in the two-phase system was stronger than that of the single phase fermentation system.